Various optical films are provided to image display devices such as liquid crystal display devices and organic electroluminescent display devices. For example, a phase difference film is sometimes provided to an image display device for achieving optical compensation of a displayed image. The optical film such as the phase difference film is produced by, for example, stretching a primary film formed of a resin to obtain a long-length film, and cutting the long-length film to a desired size (see Patent Literatures 1 to 3).